Even though Mazda recently signed an agreement with Toyota to design, engineer and produce electric and electrified vehicles, a key element of its “well-to-wheel” carbon dioxide reduction program is a compression-ignition gasoline engine family known as “Skyactiv-X”. Mazda says it will be the first commercial gasoline engine in which the fuel-air mixture ignites spontaneously when compressed by the piston.

Mazda says its proprietary combustion technology, known as Spark Controlled Compression Ignition, has a seamless transition point between compression and spark ignition, and a larger compression ignition zone. As a result, Mazda expects Skyactiv-X engines to be as much as 30% more efficient than its current gasoline engines. It not expects them to be at least as efficient, if not more efficient, than its Skyactiv-D diesel motors, but — on a well-to-wheel basis; that is, when considering the lifecycle of the vehicle and the energy needed to power it — to produce fewer carbon dioxide emissions than electric powertrains.

The Skyactiv-X engines will be supercharged, and Mazda says this and compression ignition will increase torque output 10% - 30% over its current crop of Skyactiv-G gasoline engines. In addition, fuel efficiency will be 20% - 30% greater. Plus, the broader operating band in which the engine can compress and ignite a super lean-burn fuel charge (one that is too lean for spark ignition), coupled with greater latitude in choosing gear ratios, will improve both efficiency and performance. Because the torque increase greatly expands the percentage of time in which the engine is running under low loads, this technology also will lower nitrogen oxide emissions. Spark ignition will be under higher loads.

Mazda says it plans to introduce the Skyactiv-X engines starting in 2019. At the same time, it will begin introducing electric vehicle and electrified powertrains in regions of the world that either restrict vehicles to control air pollution, or in which there is a high ratio of clean energy used for power generation. — CAS